An intercooler that cools supercharged intake air is disclosed, which performs heat exchange between the supercharged air supplied to an engine (internal combustion engine) by a supercharger and two types of cooling waters having temperatures different from each other (see, for example, Patent Literature 1). The intercooler described in Patent Literature 1 is configured in such a manner that a hot cooling water flows in an upstream part of a supercharged intake air passage where the supercharged intake air passes through while a cold cooling water flows in a downstream part of the supercharged intake air passage.
According to the configuration as above, the cold cooling water can be warmed quickly with heat of the hot cooling water at engine start-up. Further, because the supercharged intake air can be pre-cooled with the hot cooling water before the supercharged intake air is cooled with the cold cooling water, cooling performance of a supercharged intake air cooling system can be enhanced.